Asian corn borers (Ostrinia furnacalis Guenée) are important agricultural pests in the world. They mainly damage economically important crops such as corns, sorghum, sunflowers, etc. Currently, the methods for preventing Asian corn borers still mainly rely on chemical prevention. However, chemical prevention causes enormous damages to the ecology and in the safe production of foods.
The myriad problems caused by chemical prevention forces us to search for better pest management methods. Although biological prevention can produce certain preventive effects, such effects are realized slowly and are not significant. In addition, biological prevention is more susceptible to environmental impacts and is not well accepted by the public. Transgenic plants can effectively prevent pest damages. However, after long-term cultivation of a transgenic plant, insect resistance to the pesticide effects of the transgenic crop can be induced, resulting in the increase of non-targeted pests. Furthermore, the safety of transgenic plants is still in dispute, limiting further development of such technology.
Since its discovery in 1991, the phenomenon of RNAi has seen rapid development. The studies show that using RNAi from specific gene, one can achieve directed interference of a target gene, resulting in certain physiological phenomenon to accomplish the studies of gene functions. In the meantime, such phenomenon is highly specific. That is, specific fragments of homologous genes can produce different interference in different species. Therefore, this is an ideal system for the control of pests.
Currently, there are reports of using RNAi technology to control insects. Baum et al. (2007) proved that v-ATPase has a lethal effect towards Western corn rootworm (WCR) (Diabrotica virgifera LeConte) and can be used to control WCR in the field. In the same year, Mao et al. introduced a P450 dsRNA into cotton, which can cause death of cotton bollworm (Helicoverpa armigera). Tian et al (2009) proved that death of beet armyworm (Spodoptera exigua Hübner) can be induced by feeding methods. These publications all show that RNAi technology as a new pest control method is feasible.
However, prior studies also show that RNAi based pest control still has some problems that need to be overcome, such as (1) how to discover target genes with fast, high throughput methods; (2) how to simplify the applications in field production; (3) resistance problems; (4) safety issues, etc. One would need to solve the above mentioned problems in order to use the RNAi technology to control pests. First, one would need to have sufficient and effective target genes so that a large number of target genes, in different combinations, can be used at different times to target different genes to achieve pest control, thereby avoiding the formation of resistant pests. Therefore, pest controls using RNAi technology hinges on solving two urgent problems: target gene identification and how to accomplish easy application in the fields. An object of the present invention is to solve these problems.